/*
 * Tween.js
 * t: current time（当前时间）；
 * b: beginning value（初始值）；
 * c: change in value（变化量）；
 * d: duration（持续时间）。
 * you can visit 'http://easings.net/zh-cn' to get effect
*/
var Tween = {
  Linear: function (t, b, c, d) {
    return c * t / d + b;
  },
  Quad: {
    easeIn: function (t, b, c, d) {
      return c * (t /= d) * t + b;
    },
    easeOut: function (t, b, c, d) {
      return -c * (t /= d) * (t - 2) + b;
    },
    easeInOut: function (t, b, c, d) {
      if ((t /= d / 2) < 1) return c / 2 * t * t + b;
      return -c / 2 * ((--t) * (t - 2) - 1) + b;
    }
  },
  Cubic: {
    easeIn: function (t, b, c, d) {
      return c * (t /= d) * t * t + b;
    },
    easeOut: function (t, b, c, d) {
      return c * ((t = t / d - 1) * t * t + 1) + b;
    },
    easeInOut: function (t, b, c, d) {
      if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
      return c / 2 * ((t -= 2) * t * t + 2) + b;
    }
  },
  Quart: {
    easeIn: function (t, b, c, d) {
      return c * (t /= d) * t * t * t + b;
    },
    easeOut: function (t, b, c, d) {
      return -c * ((t = t / d - 1) * t * t * t - 1) + b;
    },
    easeInOut: function (t, b, c, d) {
      if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b;
      return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
    }
  },
  Quint: {
    easeIn: function (t, b, c, d) {
      return c * (t /= d) * t * t * t * t + b;
    },
    easeOut: function (t, b, c, d) {
      return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
    },
    easeInOut: function (t, b, c, d) {
      if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b;
      return c / 2 * ((t -= 2) * t * t * t * t + 2) + b;
    }
  },
  Sine: {
    easeIn: function (t, b, c, d) {
      return -c * Math.cos(t / d * (Math.PI / 2)) + c + b;
    },
    easeOut: function (t, b, c, d) {
      return c * Math.sin(t / d * (Math.PI / 2)) + b;
    },
    easeInOut: function (t, b, c, d) {
      return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
    }
  },
  Expo: {
    easeIn: function (t, b, c, d) {
      return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b;
    },
    easeOut: function (t, b, c, d) {
      return (t == d) ? b + c : c * (-Math.pow(2, -10 * t / d) + 1) + b;
    },
    easeInOut: function (t, b, c, d) {
      if (t == 0) return b;
      if (t == d) return b + c;
      if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
      return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
    }
  },
  Circ: {
    easeIn: function (t, b, c, d) {
      return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
    },
    easeOut: function (t, b, c, d) {
      return c * Math.sqrt(1 - (t = t / d - 1) * t) + b;
    },
    easeInOut: function (t, b, c, d) {
      if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b;
      return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b;
    }
  },
  Elastic: {
    easeIn: function (t, b, c, d, a, p) {
      var s;
      if (t == 0) return b;
      if ((t /= d) == 1) return b + c;
      if (typeof p == "undefined") p = d * .3;
      if (!a || a < Math.abs(c)) {
        s = p / 4;
        a = c;
      } else {
        s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
    },
    easeOut: function (t, b, c, d, a, p) {
      var s;
      if (t == 0) return b;
      if ((t /= d) == 1) return b + c;
      if (typeof p == "undefined") p = d * .3;
      if (!a || a < Math.abs(c)) {
        a = c;
        s = p / 4;
      } else {
        s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b);
    },
    easeInOut: function (t, b, c, d, a, p) {
      var s;
      if (t == 0) return b;
      if ((t /= d / 2) == 2) return b + c;
      if (typeof p == "undefined") p = d * (.3 * 1.5);
      if (!a || a < Math.abs(c)) {
        a = c;
        s = p / 4;
      } else {
        s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      if (t < 1) return -.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
      return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * .5 + c + b;
    }
  },
  Back: {
    easeIn: function (t, b, c, d, s) {
      if (typeof s == "undefined") s = 1.70158;
      return c * (t /= d) * t * ((s + 1) * t - s) + b;
    },
    easeOut: function (t, b, c, d, s) {
      if (typeof s == "undefined") s = 1.70158;
      return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
    },
    easeInOut: function (t, b, c, d, s) {
      if (typeof s == "undefined") s = 1.70158;
      if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
      return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
    }
  },
  Bounce: {
    easeIn: function (t, b, c, d) {
      return c - Tween.Bounce.easeOut(d - t, 0, c, d) + b;
    },
    easeOut: function (t, b, c, d) {
      if ((t /= d) < (1 / 2.75)) {
        return c * (7.5625 * t * t) + b;
      } else if (t < (2 / 2.75)) {
        return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
      } else if (t < (2.5 / 2.75)) {
        return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
      } else {
        return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
      }
    },
    easeInOut: function (t, b, c, d) {
      if (t < d / 2) {
        return Tween.Bounce.easeIn(t * 2, 0, c, d) * .5 + b;
      } else {
        return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * .5 + c * .5 + b;
      }
    }
  }
}
Math.tween = Tween;

/**
 * @author zhangxinxu(.com)
 * @description 让Tween.js缓动算法更容易理解和使用
 */

Math.animation = function (from, to, duration, easing, callback) {
  var isUndefined = function (obj) {
    return typeof obj == 'undefined';
  };
  var isFunction = function (obj) {
    return typeof obj == 'function';
  };
  var isNumber = function (obj) {
    return typeof obj == 'number';
  };
  var isString = function (obj) {
    return typeof obj == 'string';
  };

  // 转换成毫秒
  var toMillisecond = function (obj) {
    if (isNumber(obj)) {
      return obj;
    } else if (isString(obj)) {
      if (/\d+m?s$/.test(obj)) {
        if (/ms/.test(obj)) {
          return 1 * obj.replace('ms', '');
        }
        return 1000 * obj.replace('s', '');
      } else if (/^\d+$/.test(obj)) {
        return +obj;
      }
    }
    return -1;
  };

  if (!isNumber(from) || !isNumber(to)) {
    if (window.console) {
      console.error('from和to两个参数必须且为数值');
    }
    return 0;
  }

  // 缓动算法
  var tween = Math.tween || window.Tween;

  if (!tween) {
    if (window.console) {
      console.error('缓动算法函数缺失');
    }
    return 0;
  }

  // duration, easing, callback均为可选参数
  // 而且顺序可以任意
  var options = {
    duration: 300,
    easing: 'Linear',
    callback: function () { }
  };

  var setOptions = function (obj) {
    if (isFunction(obj)) {
      options.callback = obj;
    } else if (toMillisecond(obj) != -1) {
      options.duration = toMillisecond(obj);
    } else if (isString(obj)) {
      options.easing = obj;
    }
  };
  setOptions(duration);
  setOptions(easing);
  setOptions(callback);

  // requestAnimationFrame的兼容处理
  if (!window.requestAnimationFrame) {
    requestAnimationFrame = function (fn) {
      return setTimeout(fn, 17);
    };
  }
  if (!window.cancelAnimationFrame) {
    cancelAnimationFrame = function (id) {
      clearTimeout(id);
    };
  }

  // 算法需要的几个变量
  var start = 0;
  // during根据设置的总时间计算
  var during = Math.ceil(options.duration / 17);
  // 动画请求帧
  var req = null;

  // 当前动画算法
  // 确保首字母大写
  options.easing = options.easing.slice(0, 1).toUpperCase() + options.easing.slice(1);
  var arrKeyTween = options.easing.split('.');
  var fnGetValue;

  if (arrKeyTween.length == 1) {
    fnGetValue = tween[arrKeyTween[0]];
  } else if (arrKeyTween.length == 2) {
    fnGetValue = tween[arrKeyTween[0]] && tween[arrKeyTween[0]][arrKeyTween[1]];
  }
  if (isFunction(fnGetValue) == false) {
    console.error('没有找到名为"' + options.easing + '"的动画算法');
    return;
  }

  // 运动
  var step = function () {
    // 当前的运动位置
    var value = fnGetValue(start, from, to - from, during);

    // 时间递增
    start++;
    // 如果还没有运动到位，继续
    if (start <= during) {
      options.callback(value);
      req = requestAnimationFrame(step);
    } else {
      // 动画结束，这里可以插入回调...
      options.callback(to, true);
    }
  };
  // 开始执行动画
  step();

  return function () {
    return req;
  };
}